JP-2009-74536A (US-2009/0056677A1) shows a fuel injection system in which a fuel pressure sensor is disposed on a fuel injector in order to detect fuel pressure. Based on a variation in the fuel pressure, a variation in a fuel injection rate is estimated. Based on this estimated variation in the fuel injection rate, an actual fuel injection start timing and a fuel injection quantity are computed. The pressure sensor has a detection circuit which outputs a detection signal according to the fuel pressure. An electronic control unit (ECU) computes the fuel pressure based on voltage value of the detection signal outputted from the pressure sensor.
However, if an applied-voltage applied to the detection circuit deviates from a reference voltage, a deviation arises in a relationship between the detection signal and the actual fuel pressure, so that the fuel pressure computed by the ECU deviates from the actual fuel pressure.
Also in a case that a fuel temperature is detected by the detection circuit, a deviation between the computed fuel temperature and the actual fuel temperature will arise.